cs.hashindex 20240317

A command and utility functions for making listings of file content hashcodes and manipulating directory trees based on such a hash index.

A command and utility functions for making listings of file content hashcodes and manipulating directory trees based on such a hash index.

Latest release 20240317:

• HashIndexCommand.cmd_ls: default to listing the current directory.
• HashIndexCommand: new -o output_format to allow outputting only hashcodes or fspaths.
• HashIndexCommand.cmd_comm: new -r (relative) option.

This largely exists to solve my "what has changed remotely?" or "what has been filed where?" problems by comparing file trees using the files' content hashcodes.

This does require reading every file once to compute its hashcode, but the hashcodes (and file sizes and mtimes when read) are stored beside the file in .fstags files (see the cs.fstags module), so that a file does not need to be reread on subsequent comparisons.

hashindex knows how to invoke itself remotely using ssh (this does require hashindex to be installed on the remote host) and can thus be used to compare a local and remote tree, for example:

hashindex comm -1 localtree remotehost:remotetree

When you point hashindex at a remote tree, it uses ssh to run hashindex on the remote host, so all the content hashing is done locally to the remote host instead of copying files over the network.

You can also use it to rearrange a tree based on the locations of corresponding files in another tree. Consider a media tree replicated between 2 hosts. If the source tree gets rearranged, the destination can be equivalently rearranged without copying the files, for example:

hashindex rearrange sourcehost:sourcetree localtree

If fstags mv was used to do the original rearrangement then the hashcodes will be copied to the new locations, saving a rescan of the source file. I keep a shell alias mv="fstags mv" so this is routine for me.

I have a backup script histbackup which works by making a hard link tree of the previous backup and rsyncing into it. It has long been subject to huge transfers if the source tree gets rearranged. Now it has a --hashindex option to get it to run a hashindex rearrange between the hard linking to the new backup tree and the rsync from the source to the new tree.

If network bandwith is limited or quotaed, you can use the comparison function to prepare a list of files missing from the remote location and copy them to a transfer drive for carrying to the remote site when opportune. Example:

hashindex comm -1 -o '{fspath}' src rhost:dst         | rsync -a --files-from=- src/ xferdir/

I've got a script pref-xfer which does this with some conveniences and sanity checks.

Function dir_filepaths(dirpath: str, *, fstags: cs.fstags.FSTags)

Generator yielding the filesystem paths of the files in dirpath.

Function dir_remap(srcdirpath: str, fspaths_by_hashcode: Mapping[cs.hashutils.BaseHashCode, List[str]], *, hashname: str)

Generator yielding (srcpath,[remapped_paths]) 2-tuples based on the hashcodes keying rfspaths_by_hashcode.

Function file_checksum(fspath: str, hashname: str = 'sha256', *, fstags: cs.fstags.FSTags) -> Optional[cs.hashutils.BaseHashCode]

Return the hashcode for the contents of the file at fspath. Warn and return None on OSError.

Function get_fstags_hashcode(fspath: str, hashname: str, fstags: cs.fstags.FSTags) -> Tuple[Optional[cs.hashutils.BaseHashCode], Optional[os.stat_result]]

Obtain the hashcode cached in the fstags if still valid. Return a 2-tuple of (hashcode,stat_result) where hashcode is a BaseHashCode subclass instance is valid or None if missing or no longer valid and stat_result is the current os.stat result for fspath.

Function hashindex(fspath: Union[str, io.TextIOBase, Tuple[Optional[str], str]], *, hashname: str, hashindex_exe: str, ssh_exe: str, relative: bool = False, **kw) -> Iterable[Tuple[Optional[cs.hashutils.BaseHashCode], Optional[str]]]

Generator yielding (hashcode,filepath) 2-tuples for the files in fspath, which may be a file or directory path. Note that it yields (None,filepath) for files which cannot be accessed.

Class HashIndexCommand(cs.cmdutils.BaseCommand)

A tool to generate indices of file content hashcodes and to link or otherwise rearrange files to destinations based on their hashcode.

Command line usage:

Usage: hashindex subcommand...
    Generate or process file content hash listings.
  Subcommands:
    comm {-1|-2|-3} {path1|-} {path2|-}
      Compare the filepaths in path1 and path2 by content.
      -1            List hashes and paths only present in path1.
      -2            List hashes and paths only present in path2.
      -3            List hashes and paths present in path1 and path2.
      -e ssh_exe    Specify the ssh executable.
      -h hashname   Specify the file content hash algorithm name.
      -H hashindex_exe
                    Specify the remote hashindex executable.
      -o output_format Default: '{hashcode} {fspath}'.
      -r            Emit relative paths in the listing.
    help [-l] [subcommand-names...]
      Print help for subcommands.
      This outputs the full help for the named subcommands,
      or the short help for all subcommands if no names are specified.
      -l  Long help even if no subcommand-names provided.
    ls [options...] [[host:]path...]
      Walk filesystem paths and emit a listing.
      The default path is the current directory.
      Options:
      -e ssh_exe    Specify the ssh executable.
      -h hashname   Specify the file content hash algorithm name.
      -H hashindex_exe
                    Specify the remote hashindex executable.
      -o output_format Default: '{hashcode} {fspath}'.
      -r            Emit relative paths in the listing.
                    This requires each path to be a directory.
    rearrange [options...] {[[user@]host:]refdir|-} [[user@]rhost:]targetdir [dstdir]
      Rearrange files from targetdir into dstdir based on their positions in refdir.
      Options:
        -e ssh_exe  Specify the ssh executable.
        -h hashname Specify the file content hash algorithm name.
        -H hashindex_exe
                    Specify the remote hashindex executable.
        --mv        Move mode.
        -n          No action, dry run.
        -o output_format Default: '{hashcode} {fspath}'.
        -s          Symlink mode.
      Other arguments:
        refdir      The reference directory, which may be local or remote
                    or "-" indicating that a hash index will be read from
                    standard input.
        targetdir   The directory containing the files to be rearranged,
                    which may be local or remote.
        dstdir      Optional destination directory for the rearranged files.
                    Default is the targetdir.
                    It is taken to be on the same host as targetdir.
    shell
      Run a command prompt via cmd.Cmd using this command's subcommands.

Function localpath(fspath: str) -> str

Return a filesystem path modified so that it connot be misinterpreted as a remote path such as user@host:path.

If fspath contains no colon (:) or is an absolute path or starts with ./ then it is returned unchanged. Otherwise a leading ./ is prepended.

Function main(argv=None)

Commandline implementation.

Function merge(srcpath: str, dstpath: str, *, opname=None, hashname: str, move_mode: bool = False, symlink_mode=False, doit=False, quiet=False, fstags: cs.fstags.FSTags)

Merge srcpath to dstpath.

If dstpath does not exist, move/link/symlink srcpath to dstpath. Otherwise checksum their contents and raise FileExistsError if they differ.

Function paths_remap(srcpaths: Iterable[str], fspaths_by_hashcode: Mapping[cs.hashutils.BaseHashCode, List[str]], *, hashname: str)

Generator yielding (srcpath,fspaths) 2-tuples.

Function read_hashindex(f, start=1, *, hashname: str) -> Iterable[Tuple[Optional[cs.hashutils.BaseHashCode], Optional[str]]]

A generator which reads line from the file f and yields (hashcode,fspath) 2-tuples for each line. If there are parse errors the hashcode or fspath may be None.

Function read_remote_hashindex(rhost: str, rdirpath: str, *, hashname: str, ssh_exe=None, hashindex_exe=None, relative: bool = False, check=True) -> Iterable[Tuple[Optional[cs.hashutils.BaseHashCode], Optional[str]]]

A generator which reads a hashindex of a remote directory, This runs: hashindex ls -h hashname -r rdirpath on the remote host. It yields (hashcode,fspath) 2-tuples.

Parameters:

• rhost: the remote host, or user@host
• rdirpath: the remote directory path
• hashname: the file content hash algorithm name
• ssh_exe: the ssh executable, default SSH_EXE_DEFAULT: 'ssh'
• hashindex_exe: the remote hashindex executable, default HASHINDEX_EXE_DEFAULT: 'hashindex'
• relative: optional flag, default False; if true pass '-r' to the remote hashindex ls command
• check: whether to check that the remote command has a 0 return code, default True

Function rearrange(srcdirpath: str, rfspaths_by_hashcode, dstdirpath=None, *, hashname: str, move_mode: bool = False, symlink_mode=False, doit: bool, quiet: bool = False, fstags: cs.fstags.FSTags, runstate: cs.resources.RunState)

Rearrange the files in dirpath according to the hashcode->[relpaths] fspaths_by_hashcode.

Parameters:

• srcdirpath: the directory whose files are to be rearranged
• rfspaths_by_hashcode: a mapping of hashcode to relative pathname to which the original file is to be moved
• dstdirpath: optional target directory for the rearranged files; defaults to srcdirpath, rearranging the files in place
• hashname: the file content hash algorithm name
• move_move: move files instead of linking them
• symlink_mode: symlink files instead of linking them
• doit: if true do the link/move/symlink, otherwise just print
• quiet: default False; if true do not print

Function run_remote_hashindex(rhost: str, argv, *, ssh_exe=None, hashindex_exe=None, check: bool = True, doit: bool = None, quiet: Optional[bool] = None, options: cs.cmdutils.BaseCommandOptions, **subp_options)

Run a remote hashindex command. Return the CompletedProcess result or None if doit is false. Note that as with cs.psutils.run, the arguments are resolved via cs.psutils.prep_argv.

Parameters:

• rhost: the remote host, or user@host
• argv: the command line arguments to be passed to the remote hashindex command
• ssh_exe: the ssh executable, default SSH_EXE_DEFAULT: 'ssh'
• hashindex_exe: the remote hashindex executable, default HASHINDEX_EXE_DEFAULT: 'hashindex'
• check: whether to check that the remote command has a 0 return code, default True
• doit: whether to actually run the command, default True Other keyword parameters are passed therough to cs.psutils.run.

Function set_fstags_hashcode(fspath: str, hashcode, S: os.stat_result, fstags: cs.fstags.FSTags)

Record hashcode against fspath.

Release Log

Release 20240317:

• HashIndexCommand.cmd_ls: default to listing the current directory.
• HashIndexCommand: new -o output_format to allow outputting only hashcodes or fspaths.
• HashIndexCommand.cmd_comm: new -r (relative) option.

Release 20240316: Fixed release upload artifacts.

Release 20240305:

• HashIndexCommand.cmd_ls: support rhost:rpath paths, honour intterupts in the remote mode.
• HashIndexCommand.cmd_rearrange: new optional dstdir command line argument, passed to rearrange.
• merge: symlink_mode: leave identical symlinks alone, just merge tags.
• rearrange: new optional dstdirpath parameter, default srcdirpath.

Release 20240216:

• HashIndexCommand.cmdlinkto,cmd_rearrange: run the link/mv stuff with sys.stdout in line buffered mode.
• DO not get hashcodes from symlinks.
• HashIndexCommand.cmd_ls: ignore None hashcodes, do not set xit=1.
• New run_remote_hashindex() and read_remote_hashindex() functions.
• dir_filepaths: skip dot files, the fstags .fstags file and nonregular files.

Release 20240211.1: Better module docstring.

Release 20240211: Initial PyPI release: "hashindex" command and utility functions for listing file hashcodes and rearranging trees based on a hash index.